What is so wrong with not wanting people in America illegally?

The clue is in the words: "illegally".

Surely you should be preventing illegal things from occurring? So I don't see it as wrong at all.

The main issue is that the US has stupid immigration laws. This is compounded by the fact that a lot of people don't appear to understand the difference between legal immigration and illegal immigration.

The laws are silly because if you try to enter the US legally and your paperwork is not in order you can be sent straight back home. On the other hand, if you enter illegally, with no paperwork at all, then you need to be accommodated while you wait for your trial then you need to attend the trial and then get all your details checked out: are you a criminal, were those children you came with actually yours, are your asylum claims valid? All that takes time, money and staff - including judges, attorneys, law enforcement etc.

When people are arriving at the rate of 50,000 a month then the costs soon start to mount up and the accommodation situation becomes very difficult.

Obama knew that better laws were required so he chose to not enforce the law (He was not supposed to do that!). You were told to come back for your trial in a few days. So once you were in you could stop as long as you liked if the authorities could not find you. In a sanctuary city you could continue to commit crimes and you would most likely not be sent home.

https://www.youtube.com/watch?v=kBTHODw0WtY

Right

So give them due process already, instead of keeping them in dessert camps and stealing their children.

Nothing. We just object to your solutions. And I've always wondered why you don't advocate punishing the employers who hire undocumented workers? If they stopped offering jobs, the people would stop coming.

Why did you enter me illegally

Alright, pack your bags and go back to Germany, England, France...wherever you people are from.

It seems heartless on the surface, but not all of them are nice people or will assimilate well.